US patents for RFID issued before January 1, 2009 were researched for RFID essential patent candidates. Essential Patent for RFID is an issued patent such that one　 or more of its claims is necessarily infringed by a product designed to implement the relevant UHF RFID standards: the EPCglobal Air Interfaces Standards Gen1 and Gen2 and ISO/IEC 18000-Part 6 (including Amendment 1) and the communications and interface protocols and conformance specifications referred to in those documents.

In our research, the RFID protocols are mined: encoding/decoding of communication signal /data layout of tag memory, air interface protocol, anti-collision protocol, and modulation protocol.

Top 5 contenders in RFID essential patent licensing are Micron Technology, Intermec, Motorola, Impinj, and IBM.